The present invention relates to an apparatus and method for forming laminar sheet or sheeting materials useful as upholstery and, more particularly, to sheet material having transversely extending overlay straps of dielectrically heat sealable material bonded thereto.
The laminar sheet materials may be formed of plastic and/or fabric layers of conventional composition as described below in greater detail, and the base material and strap material may be provided with a woven or non-woven fabric backing. Accordingly, the base material and/or the strap material may comprise a single or multi-ply construction. A wide range of plastic and fabric materials may be used provided the strap material is dielectrically heat sealable to the base material.
The laminar sheet materials are preferably relatively flexible and provided in roll stock form for convenience of use in subsequent applications. Accordingly, the laminar sheet materials are themselves formed of flexible base sheet materials and overlay strap materials which require web-type handling procedures and present special dielectric sealing problems. Thus, the production of the laminar sheet materials requires an efficient combination of the web handling and dielectric sealing techniques to provide an economically satisfactory product. The transverse orientation of the overlay strap material with respect to the length of the base sheet material is a further constraint in the economic resolution of these problems, since it requires an intermittent sealing procedure.
The dielectric heat sealing of plastic materials to provide decorative upholstery materials is known, and a variety of techniques may be used to form such materials in a continuous manner when continuous layers of materials are bonded or sealed in a lengthwise or machine direction. However, the provision of lengthwise discontinuous or transversely extending bonding and layers is typically only achieved through manual operator layup techniques. The use of manual layup or positioning techniques for lengthwise discontinuous layers is often the result of the difficulties in handling finite lengths or inserts of plastic materials due to their inherent tendency to curl, coil, or otherwise assume a nonplanar configuration. The discontinuous layers or strap material herein is typically provided by cutting a large web of material to proper dimensions, and the tendency to assume a nonplanar configuration is associated with the stresses resulting within the cut material.
An automated apparatus and method for dielectric sealing and embossing of a plastic thread in a transverse direction across the width of a base material are disclosed in U.S. Pat. No. 2,994,360, assigned to the assignee herein, the teachings of this patent being incorporated by reference. In this prior art technique, a thread feed mechanism traveling along a circular path is used to grip the ends of a length of thread which is to be dielectrically sealed to the base material in order to align the thread and pregrip the thread end adjacent the thread supply for use in the next dielectric sealing cycle.